Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
#define ll long long
using namespace std;
const ll INF=(ll)1e9;
const ll MOD=(ll)1e9+7;
vector<int> dx={1,0,-1,0},dy={0,1,0,-1};

int main(){
  int H,W,cnt=0;
  cin>>H>>W;
  char c[H][W];
  int d[H][W];
  for(int i=0;i<H;i++){
    for(int j=0;j<W;j++){
      cin>>c[i][j];
      if(c[i][j]=='.') cnt++;
      d[i][j]=INF;
    }
  }
  int gx=W-1,gy=H-1;
  queue<pair<int,int>> q;
  q.push(pair<int,int>(0,0));
  d[0][0]=0;
  while(q.size()){
    pair<int,int> p=q.front();
    q.pop();
    if(p.first==gy&&p.second==gx){
      cout<<cnt-d[gy][gx]-1<<endl;
      return 0;
    }
    for(int i=0;i<4;i++){
      int nx=p.second+dx[i],ny=p.first+dy[i];
      if(0<=nx&&nx<W&&0<=ny&&ny<H&&d[ny][nx]==INF&&c[ny][nx]=='.'){
        q.push(pair<int,int>(ny,nx));
        d[ny][nx]=d[p.first][p.second]+1;
      }
    }
  }
  cout<<"-1"<<endl;
}